The external tool could not draw the message flows.
The reason why the message flows are missing is that Bonita does not export the Diagram Interchange (DI) information (graphical position information) for message flows. At least it’s missing in the "Onboarding2.bpmn" file. So the problem in these cases is with Bonita, this is how they export.
Also Bonita could not import XML created by their own exporter.
It seems that there are some incorrect and unstructured elements in their XML.